放射性コンシューマプロダクトの線量評価

―光学顕微鏡―

抄録

Some consumer products contain small amounts of radioisotopes, which called radioactive consumer products. The benefit of the radioactive consumer products must greatly exceed the risk of radiation from them. Moreover they have to be safe for public even after disposal. In this study, we have evaluated safety of an optical microscope that contains radioactivities in its prisms and an objective lens. Aγ-ray analysis of the prism using pureGe-multichannel analyzer reveals that there exist radioactivities of thorium series in it at concentration of 7.6% by the weight. Radioluminographic images of them were taken by FLA-2000 using an imaging plate. The results showed that thorium series were contained uniformly in the glasses. Dose equivalent rates at the surface and at the point of 1 m from the head of this microscope were measured by film badges (FB) and pocket dosimeters, respectively. If we used them 240 hours (=1h×20 days×12months), the result of FB showed under detection limit (0.1mSv) .However, dose equivalent rate at 1 m led about 420μSvper year after subtracting natural radiation if we stayed just there for one year (=24h ×365day) .
Although the outcomes of these evaluations of radiation exposure had little problems under the normal conditions, users had a right of determination to use or not to use these radioactive consumer products. So manufacturers have to express their products as radioactive consumer products.